This invention relates to an audio mixing circuit for use in audio mixing consoles (audio mixers) or the like.
FIG. 4 shows a block diagram of one exemplary arrangement of conventional audio mixing consoles.
As shown in FIG. 4, an audio mixing circuit making up an audio mixing console includes a head amplifier 15, an equalizer 16, a fader 17, and a pan circuit 18. It is also shown in FIG. 4 that two more audio mixing circuits each having the same circuitry as described above are provided as indicated each by a broken line drawn like a box.
An audio signal impressed at an input terminal 14 is amplified to a prescribed level by the head amplifier 15, and a timbre thereof is then adjusted by the equalizer 16. Thereafter, the signal output from the equalizer 16 is given to the fader 17, usually constructed of a variable resistor, in which a volume thereof is adjusted. The signal output from the fader 17 is fed to the pan circuit 18, and is divided therein into a left channel bus (BUS) 19 and a right channel bus (BUS) 19 in a proportion determined according to a desired location of the final output sound.
The input and output signals of the fader 17 are also transmitted through a changeover switch to an external channel AUX 22. As illustrated in FIG. 4, the changeover switch is comprised of three terminals, which includes a pre-fader terminal 20 connected to the input of the fader 17, a post-fader terminal 21 connected to the output of the fader 17, and a terminal connected to the AUX 22. The AUX 22 is connected to an external reverb circuit 23, in which a reverberation component is obtained from the input signal. The reverberation signal output from the reverb circuit 23 is fed through the input terminals 24, 25 to both of the two separate audio mixing circuits each indicated by a broken line drawn like a box, and signals output from these audio mixing circuits are added respectively to the original signals in the BUS 19. The above-described arrangement of the conventional audio mixing consoles is disclosed for example in John M Eargle, “HANDBOOK OF RECORDING ENGINEERING”, 1986, Van Nostrand Reinhold Company, Inc., New York, U.S.A.
The function of the audio mixing circuit in the above-described conventional audio mixing console is for example to adjust a timbre, volume, sense of direction, sense of distance of an input sound by manipulating the equalizer 16, fader 17 and pan circuit 18. Among these elements to be adjusted, the sense of distance is adjusted by regulating a volume and timbre of the sound, and a ratio of energy between direct and indirect sounds in accordance with the distance. However, in order to produce such a natural sense of distance as if a sound source is moving away, only to individually manipulate each of the above-recited elements to be adjusted is not sufficient. Rather, disadvantageously, lowering the volume of the sound, attenuating a high-audio-frequency component assumed to be absorbed in air (see Junichi Maekawa, Masayuki Morimoto, Kimihiro Sakagami, “KENCHIKU-KANKYO ONKYO-GAKU (Architectural-Environmental Acoustics)”, Second Edition, Sep. 25, 2000, Kyoritsu Shuppan, Co. Ltd., Tokyo Japan; pp. 53, 97), and lowering the ratio of a direct sound to an indirect sound all should be carried out simultaneously.
When these operations are to be carried out simultaneously on a conventional audio mixing circuit, to be more specific, distance attenuation (uniform attenuation throughout all audio frequencies) of the sound should be performed using the fader 17, and attenuation of high-audio-frequency components of the sound should be performed using the equalizer 16, and the ratio of a direct sound to an indirect sound should be adjusted by generating an indirect sound component in the reverb circuit 23 from a signal transmitted from the pre-fader terminal 20 through the AUX 22 and transmitting the resultant signal to the other two audio mixing circuits (as indicated by broken lines in FIG. 4) to regulate a ratio of the indirect sound component to be mixed with the original signal.
To adequately adjust the sense of distance of the output sound, the equalizer 16, fader 17 and AUX 22 (quantity of signals transmitted therethrough) are all to be synchronously manipulated in a correlated manner. However, such synchronous operation of these three elements real-time is so difficult that, in actuality, operation of one of these elements, e.g., equalizer 16, should have unavoidably been omitted. Accordingly, natural transition of sense of distance could not be achieved in most instances.
Although the above description has been directed to one example of adjusting a sense of distance in the output sound to one that sounds as if a sound source is moving away, the same problem would come up on adjusting a sense of distance to one that sounds as if the sound source is approaching; i.e., the equalizer 16, fader 17 and AUX 22 (quantity of signals transmitted therethrough) all should disadvantageously be manipulated synchronously in a correlated manner, which is close to impossible.
The present invention has been made to address the above-discussed disadvantages.